Actually, you should look at margins, not vote share

When it comes to polls, 50 percent is just another number

You often hear pollsters say that a candidate’s vote share is more important than the margin between the two candidates in a given poll. That’s not always true. And it’s not at all true in a presidential race like this one, where the candidates are divided by less than 2 points across all the battlegrounds.

The race is a pure tossup, even if one candidate hits 50 percent in a state poll from time to time.

What I’ll call The 50 Percent Myth is mostly a superstition that’s grown up among gut-driven political consultants, something that has no basis in statistical probability. Pollsters will use a focus on vote share to explain away a poll that called the winner or the final margin wrong, but got the vote share for their candidate right (likely by coincidence).

From what I can tell, I’m the rare professional pollster who doesn’t put much stock in vote share—except as a byproduct of the margin and a survey’s share of undecided voters.

We’ve seen pieces about this written about recently by C…